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support transparent images

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This commit is contained in:
Markus Teich
2015-12-08 21:46:18 +01:00
parent b516f468fa
commit 0798e82d23
1 changed files with 16 additions and 3 deletions
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19
sent.c
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@ -215,6 +215,8 @@ int ffread(Image *img)
{
uint32_t y, x;
uint16_t *row;
uint8_t opac;
uint8_t fg_r, fg_g, fg_b, bg_r, bg_g, bg_b;
size_t rowlen, off, nbytes;
ssize_t r;
@ -239,6 +241,11 @@ int ffread(Image *img)
return 0;
}
/* extract window background color channels for transparency */
bg_r = (sc->bg.pix >> 16) % 256;
bg_g = (sc->bg.pix >> 8) % 256;
bg_b = (sc->bg.pix >> 0) % 256;
for (off = 0, y = 0; y < img->bufheight; y++) {
nbytes = 0;
while (nbytes < rowlen) {
@ -248,9 +255,15 @@ int ffread(Image *img)
nbytes += r;
}
for (x = 0; x < rowlen / 2; x += 4) {
img->buf[off++] = ntohs(row[x + 0]) / 257;
img->buf[off++] = ntohs(row[x + 1]) / 257;
img->buf[off++] = ntohs(row[x + 2]) / 257;
fg_r = ntohs(row[x + 0]) / 256;
fg_g = ntohs(row[x + 1]) / 256;
fg_b = ntohs(row[x + 2]) / 256;
opac = ntohs(row[x + 3]) / 256;
/* blend opaque part of image data with window background color to
* emulate transparency */
img->buf[off++] = (fg_r * opac + bg_r * (255 - opac)) / 256;
img->buf[off++] = (fg_g * opac + bg_g * (255 - opac)) / 256;
img->buf[off++] = (fg_b * opac + bg_b * (255 - opac)) / 256;
}
}